1. Field of the Invention
The present invention comprises a closure and container combination or package. More specifically, the present invention provides a package having a closure including drafted threads and a complimentary container neck having at least one complimentary drafted thread.
2. Description of the Related Art
Various closure and container combinations or packages have been developed for instance to provide a means for sealably engaging a container neck and inhibiting leakage therefrom. As shown in FIG. 1, many closures or caps utilize a tapered skirt, from smaller upper diameter to larger lower diameter, in order to more easily remove the closure from the mold core during de-molding. For example, closures may be tapered about one to two degrees. However, it may be desirable to increase the taper in order to further reduce the difficulty with removing a closure from a mold.
In addition to the tapered skirt, drafted or tapered closure threads have been utilized in order to provide additional aid to removal of the closure from the mold core during manufacture. The tapered closure threads typically have been about ¼° (degree) or more of draft in order to reduce torque during removal of the closure from a mold core in the manufacturing process. Without such taper, a constant and continuous torque is required to remove the closure from the mold core. Thus, the drafted closure threads and tapered closure skirt, in combination, provide for improved removal of the closure from the tooling.
However, this tapered closure skirt and thread design has resulted in several problems. First, since the closure skirt is tapered and extends away from the container neck, the threads of the closure and container lose engagement farther down the neck as depicted. More specifically, FIG. 1 depicts thread engagement lengths T1-T4, measured in a radial direction. T1 is shown at the top of the package having the largest engagement length, measured in a radial direction, while T4 is shown at the bottom of the package having the shortest engagement length due to the taper of the closure skirt away from the container neck finish. Decreasing engagement of the closure threads and container threads is highly undesirable and results in stripping and loosening of the closure and container threads.
One means for overcoming this problem is to taper the bottle neck to match the taper of the closure skirt and threads. But, since most bottle necks are molded utilizing a mold core and cavity tooling, tapering the bottle neck makes it impossible to remove a bottle neck from the mold. In order to overcome this molding issue, it might be possible to utilize a parallel sided core producing a non-uniform neck wall however, this is a cost prohibitive manufacturing technique due to added material and longer processing cycle.
Given these deficiencies a structure is needed which overcomes these problems providing increased engagement of closure and container threads along the axial length of the container neck.